Recently, due to problems such as a rapid rise in oil prices, an environmental problem of the earth, exhaustion of fossil energy, waste treatment in nuclear power generation, position selection according to construction of a new power plant, etc., interest in renewable energy has increased and among others, research and development for a solar cell, which is a pollution-free energy source, has actively been progressed.
The solar cell, which is a device converting light energy into electrical energy using a photovoltaic effect, has recently been receiving much attention according to an increased demand of alternative energy.
In the solar cell, it is important to increase conversion efficiency that is associated with a rate of converting incident sunlight into electric energy. Various researches to increase the conversion efficiency have been progressed and research to increase a rate of sunlight absorbed into the solar cell by reducing light loss as much as possible so as to increase the efficiency of the solar cell has been progressed.